Electric alarm signaling system



Nov. 30, 1948.

Filed Kay 1. 1943 E. COHRT ELECTRIC ALARM SIGNAL ING SYSTEM 4 Sheets-Sheet 1 -Gui'2 Gura Gur5 GAN

INVENTOR -v GENT.

Nov. 30, 1948- E. COHRT 2,454,775

ELECTRIC ALARM SIGNALING SYSTEM Filed may 1, 1945 4 Sheets-Sheet 2 v d y, 3 s

- u. l 11' TI. H 5. T J i qEfII I! I." :5 YO 7 H 9 l: INVENTOR 1576/4 CO/Y/PT BYWY 6E NT."

Nov. 30, 1948. E. coHRT ELECTRIC ALARM SIGNALING SYSTEM 4 Sheets-Sheet 3 Filed May 1, 1943 Y. O INVENTOR [/61 Col/87 37 GENT.

Nov. 30, 1948. E. COHRT 2,454,775

ELECTRIC ALARM SIGNALING SYSTEM Filed llay 1, 1943 4 Sheets-Sheet 4 i Ipra Ipn INVENTOR [76/4 comer RL+ RL3 RL2 RLI T 1 1 ENT Patented Nov. 30, 1948 ELECTRIC ALARM SIGNALING SYSTEM Eigil Cohrt, Copenhagen, Denmark, assignor to International Standard Electric Corporation, New York, N. 2., a corporation of Delaware Application May 1, 1943, Serial No. 485,405 In Denmark July 13, 1940 '7 Claims.

The present invention relates to a telephone system, containing means for establishing a connection from an exchange to a plurality of subscribers simultaneously, for instanceby alarm, and one object of the invention is to provide such a telephone system, which is reliable and simple. and in which it is possible to converse from an exchange over the telephone with each of the subscribers, and the subscribers or certain groups of subscribers may be called simultaneously.

Another object of the invention is to provide a telephone system applicable, for instance, to a fire alarm system in a smaller town, where the firemen are not constantly on duty at the firestation, but the latter is provided. with a telephone command-station from which lines extend to the private homes of the firemen so that any individual line may be chosenfor conversation with a selected fireman, or, alarm calls may be made to a selected group of firemen orto all the firemen simultaneously.

These and other objects are accomplished, according to the invention, by the arrangement and combination of elements set forth in the following description, defined in the appended claims and illustratively exemplified in the accompanying drawings, in which i Fig. l is a circuit diagram for a commandstation;

Fig. 2 is a diagram of a distributing circuit common to a group of subscribers;

Fig. 3 is a diagram of a subscribers line circuit;

Fig. 4 is a diagram of a common circuit serving all the subscribers; and

Fig. 4a is a diagram of a further circuit serving a group of subscribers.

Fig. 5 is a diagram of a circuit for a subscribers telephone.

Operation of the system in general The drawing shows an alarm system for the transmission of telephone messages from a command-station at a fire-station to a maximum of thirty firemen at their private homes. The system permits ordinary telephone conversation be tween the command-station and the firemen singly, whereas conversation between the firemen is impossible. Nocalls can be made from the firemen. At alarm, which may be made either in groups with a maximum of eight firemen to a group or as general alarm, the firemen cannot talk to the command-station, but acknowledge receipt of the message by depressing a key on their telephone.

Ill)

The subscriber telephones are connected to the command-station through direct lines.

Ordinary telephone conversation A talking key TN, Fig. 1, corresponding to the wanted line, e. g. TNl, is depressed, whereby automatic ringing, i. e. about 2 seconds ringing'takes place about every fifth second and a corresponding call back signal is sent to the telephone apparatus of the command-station.

When the called subscriber answers, the ringing and the call back signal cease, and an answer lamp SL, indicating that the connection has been established, is lighted whereupon the conversation may take place. i Y

When the conversation is finished, the key TN is restored, whereupon the connection is' interrupted. It should be noted that when the lamp SL has once been lighted, it remains illuminated until corresponding key TN has been restored.

Alarm One or more group keys GN, or in case of general alarm, a general alarm key GAN is depressed, whereupon automatic ringing is sent'out' to all the corresponding lines. a

In order to distinguish between alarm and ordinary calls, the ringing consists in the case of alarm of two double ringings each lasting about /2 second every fifth second.

An amplifier is inserted between the telephone apparatus of the command-station and therelay equipment.

When the various firemen answer, the corresponding lamps SL are lighted, and the message may be given. It is not necessary that allthe firemen have answered before the message is sent, the ringing being continued on the other lines which are automatically connected to the command-station as they answer.

The firemen acknowledge receipt of the message by depressing an acknowledge key KNon their telephone apparatus, whereby a corresponding acknowledge lamp KL is lighted on the command-s'tation.

When the keys GN or GAN are restored all the relays are released, and the command-station may make a new alarm.

Detailed description of the operation at an ordinary telephone conversation It the operator at the fire-station wants to talk to a certain fireman, the individual talking key corresponding to this firemans line, e. g. key TN1, is depressed, whereby earth is connected 3 to battery over the winding of a corresponding calling relay Sin and also across the slow working right middle back contact of this relay over the winding of a ringing relay Ron, and the latter is energized before the relay Stn has interrupted said back contact.

Relay Ron is looked over a separate winding and its right inner front contact to battery on relay Stns fast working outermost right front contact which is closed before the slow working back contact is interrupted. RelayStn connects earth to the charging circuit (not shown) so that charging of the battery isinterrupted .during the conversation.

As all the keys TN are connected in series, it will be seen that these keys cannot be used to energize two or more calling relays Str simultaneously, so that connection between two different firemans lines is prevented.

Ringing Over theoutermostleft front contacts of each of the relays Str and R01, a circuit is closed for a common relay Rsr'which starts the ringing ma- .chine :RM and further .connects earth to the .windingofa rel-ayIpTrviathe-back contact of a .;relay;Ipr2. Uponenergization of the relayilpri a circuit is closed for the relay Iprz which attracts .-slowly;in order-torgive relay Ipri time for being saturated, as this re1ay is to release 'slowly'when relayrlprz interruptsits back contact. Over the :frontzcontact of relaylprz acircuit isuclosedfor thermagnetSM-of a step byxstep selector, and the 'magnetarmature is attracted. When relay Ipn is deenergized, it interrupts thelcircuit for relay lprz' which breaks the circuit 'fOI the" magnet SM. Thearmatureof-SM releases andthe step by "step rselector advances (one step. When "relay Iprz rcl'oses its .:back contact, relay :I'pn "is energized again, and the same cycle is repeated so that the step by step selectonadvances step by step and stops second on each contact, as long as relay Rsriremains energizedcover 'the "front 'con- .tacts .of .1 any relay; pair :Str, 'Rcr.

. At the! outermost. right back contact :of aconverter relay For, earth .is ,connected :to the 1) brush of the .step'by step selector, SDlth'ELtfa, ringing::transmitter;relay.=Rr .is 'energizedrwhile the .fstepvby-"step: selector SMpasses-its bank contacts 2 to 1. Ringing is sent to the selected linein the :following circuit: :source. of "ringing current "individual ringing lamp 'RLI', :a :front contact of the common ringing transmitter relay Rryright middle back contact=of::an individual alarm relay Garnleft outermost front contact of the energized zringingrelay R0171, -l80 ohms windin'g .on an individual answer relay Bri, a wire L2, a bell in the :telephone apparatus, a wire L1, right middle front :contact :of the :relay Ron :and :to earth. .The answer relay Bruin-the ringing-circuit remains deenergized asilong as "this circuitis closed over the-bell .in the subscribers ttelephone.

:Two :seconds ringingis ithus given 5 every :fifth second until anfanswerisreceived ,or untilithe key TN1 is restored.

Call back signal is sent tothetelephone apparatus-of the command-station over a call back circuit connecting the main line and its telephone apparatus to the ringing circuitzthroughthe inner front contacts.of:relay.Str1,.a MF condenser I and .the outermost .right front contact of the ringing relay .Rcri.

.Answer Whenthe called fireman removes the. re ei e .between two ringings, the relay Brr is energized from battery on the back contact of the ringing transmitter relay RT.

The release 'of'the ringing relay Rcrr puts the line through to the command-station through two condensers and interrupts the call back signal.

The telephone apparatus of the command-station receives microphone current from an induction coil RC, whereas the connected subscriber apparatus receives microphone current through the answer relay B71 in the following circuit: earth,

.left innermost aback contact 'of the correspondingalarm relay Gan, left .180 'ohms winding'on relay 'Br1,.'right back .contact'on relay Ran, the wire .L1, the telephone apparatus, the wire L2,

right ohms winding onrelay .Bri, outermost leftback "contact :on relay RCTI, outermost left Answer relaysBriywhich is now energized in the above'mentioned 'circuit, closes azcircuit for the repeater relay Kim, which is'energized slowly .and'makes battery connection over the left out- When the relay"Rcrris released, the 'circuit'for the common relay 'Rsr is interrupted, and "this relayreleases'andinterrupts 'the circuits for the relays'Ipn, Iprzand'R'rxwhich all release.

From th'e outermost left back contact of relay "Rsr :earth is then connected :to the contacts in the contact bank a and through the:brush a and the magnet'of the step by-step selectoris energized :over the break contact ofzthe'latter, whereby its armature is attracted. "Immediately thereafter,

- :the break contact interrupts'the circuit so that the armature is released and the step by step selector advances one step, after which the'break contact is closed again. The step by step selector moves to normal position. where the magnetization circuit is definitely interrupted.

Release When the conversation is finished the key TN1 is .restoredxso that relay Sin is "released together with the relays BTl and Kvripafter which all the relays are againin their normal positions.

Alarm At alarm, one or more of the groupkeys'GN, ae or, in case of a general alarm, the general alarm keyGAN is depressed. I :A group callingmelay Gur .ae.corresponds to .each key .GN act-c, .respectively, :and controls a group ofat most-eight. lines.

had 'been depressed. The "relays :Rcr rare locked and cause transmission of ringing current.

The common converter relay For is :energize'd by acircuit from earth over the keys GN or GAN and inserts an amplifier (not shown) which is started from one of its front contacts.

' Ringing When an alarm relay, e. g. Gan, is energized the call back circuit is interrupted at the outermost right back contact of this relay Gan, and the ringing itself is derived over the middle right front contact of the latter The relay Rsr in the common circuit is energized, and the step by step selector advances step by step as already explained, but since the converter relay For is energized there is earth on the brush instead of on the brush b.

, In order to decrease the load on the ringing machine the ringing contacts for the various groups in the 0 bank are displaced relative to each other, so that ringing ismade to one group only at a time. In case of group a, for instance, a group ringing relay Grm is energized from the contacts |-2 and 5--6 of selector bank 0 whereby double ringing is made about every fifth second.

Answer As each fireman of the group called takes off .his receiver, the corresponding answer relay B1 is energized as mentioned and interrupts the locking circuit for the associated ringing relay Rc-r which releases, but the relay Br cannot remain energized, because battery is now connnected to its left winding from the innermost left front con tact of the associated relay Gar. Each relay B1 is therefore released again before the corresponding repeater relay Ker has had time to operate.

As both of the windings of the answer relay B1 are now connected to battery, no microphone current is supplied to the subscriber apparatus so that it is not possible to talk from it and thereby disturb the message.

The answer lamp SL is lighted over the outermost left hand front contact of the relay St? and the back contacts of relays R01 and B1" and indicates thereby that the fireman is ready to receive the message which is sent from the commandstation by means of the amplifier.

The two 200 ohms resistances inserted in the talking line serve for preventing disturbances, for instance from a short-circuited line.

Acknowledgement When the message has been received the fire man acknowledges the receipt by depressing for a moment an acknowledge key KN of his telephone apparatus, whereby earth through an induction coil is connected to the wire L1 and energizes the corresponding answer relay Bn through its left winding. The repeater relay Ken is energized from the front contact of relay Em and is looked over the innermost right front contact of relay Gan, as relay B11 is again released when the key KN is restored. Relay K'UTl connects battery to the acknowledge lamp KL1 which is lighted at the command-station.

When all the firemen have acknowledged the receipt of the message, the key or keys GN, or possibly the key GAN, are restored, and all energized relays are released, after which the system is ready for another alarm.

I claim:

1. In a telephone system with alarm device having a command-station, a telephone at said command-station, a two wire main line connected to said telephone at said command-station, a plu rality of two wire subscriber lines and a plurality of subscriber telephones each including a bell circuit connected across the associated subscribers line when said subscribers telephone is in its inoperative position and a microphone circuit substituted for said bell circuit across said subscribers line when said subscribers telephone assumes itsoperative position, the combination of a calling circuit for each individual subscriber, individual talking keys at said command-station to close each of said calling-circuits, a calling relay in each of said calling circuits to connect,

upon being energized, the called subscribers line to the main line, a ringing machine common to all subscribers, a ringing circuit for each subscriber adapted to' be connected to said common ringing machine, an answer relay for each subscriber, a ringing relay for each subscriber, an energizing circuit for each ringing relay including a slow working back contact of said calling relay, a stick circuit for each ringing relay containing a back contact of the corresponding answer relay and a fast working front contact of said calling relay, said ringing relay being adapted to break the subscribers line intermediate said calling relay and the subscribers telephone and to connect said ringing circuit through a winding of the answer relay to the part of the subscribers line connected to said telephone, each answer relay being adapted to remain deenergized when a circuit through its winding is closed over the corresponding bell circuit and to become energized when it is traversed by current flowing through the subscribers microphone circuit, a source of microphone current for each subscribers telephone, a microphone current circuit connecting said source of microphone current across the corresponding subscribers line over a winding of said answer relay, a back contact of the ringing relay and a front contact of the calling relay, a number of group keys at said command-station, a number of group calling relays each energized upon operation of the corresponding group key to close a predetermined group of calling circuits, and an alarm relay for each subscriber energized over a front contact of the corresponding group calling relay, each alarm relay having a back contact inserted in the corresponding microphone current circuit.

2. A system, as claimed in claim 1, including for each subscriber a call back circuit connecting the main line in parallel with the selected subscribers telephone and in series with a winding of said answer relay to the selected ringing circuit over front contacts of the corresponding calling and ringing relays and at least one back contact of the corresponding alarm relay.

3. A system, as claimed in claim 1, including, at said command-station, an answer signal for each subscriber, and means to energize each answer signal alternatively over a front contact of the corresponding calling relay and back contacts of the corresponding ringing relay and answer relay when the latter is deenergized or over a back contact of the correspondng alarm relay when said answer relay has been energized for a predetermined length of time.

4. A system, as claimed in claim 1, including a general alarm key at the command-station t0 energize all said group calling relays simultaneously.

5. A system, as claimed in claim 1, comprising a common converter relay, means to energize said converter relay upon actuation of any of said group keys, an amplifier, and means controlled bysaid converter rrela-y to :insert said amplifier "into said main line.

6. ;A.- system, as claimed in claim 11, including-a step 'by step selectorhavin'gza firstrandxa second brush and associated 'contact banks, means for rotating said step by step selector as-long as a ringing relay is energized, a common ringing -relay:.upon actuation of any of said group keys,

a ,circuit for intermittent energization of said ringing transmitter relay-over said contactrgroup in;said first bank, the'first brush and .a back :contact of said converter relay, and circuits for intermittent and successive energization of said group ringing relays over the corresponding contact groups of said second bank, said second brush and a front contact of said converter relay, each of. said ringing circuits being connected with said ringing machine selectively over a front contact of said ringing transmitter relay and a back contact of the corresponding alarm relay or over a front contact of the associated groupringing relay and a front contact of the corresponding alarm relay.

' 7. A.- system, as rclaimediin :claim 1, z'including', ineach subscri'bers telephone, an acknowledge key adaptedto-close an energizingcircuit for-said answer relay over one wire of the associated subscribers line, a back contact of the associated ringing relay and a front contact ofthe associated alarm relay, an acknowledge signal fo'r each subscriber at said command st'ati'on, and means to actuate each-acknowledge s-ignalc'over a front contact of the associated sal-ar'msi gn'al when said answer relay has' been energized-Ker a predeterminedlength of time.

EIGIL COHRT.

REFERENCES CITED The following .references'are ofrecorddn'the file .of this patent:

UNITED STATES :PAIENTS Number Name Date 830,981 Dyson Sept. 11, 1906 1,569,430 Loin-ax Jan. 12, 1926 1,714,303 Friendly 'May 21,1929 2,386,126 Lomax s Oct. 2, 1945 OTHER REFERENCES Telephone Communication-Systems, by "Kloe'ffler, page 85, MacMill'an PublishingCo, '1'22'5. 

